Hundreds of birds—including this loon pictured on the Oregon coast—are washing up on the shores of the U.S. Pacific Northwest coated with a foamy sea slime, scientists say.

The slime, which comes from algae blooms in the ocean, saps the waterproofing ability of the birds' feathers, experts say. Untold hundreds have died, succumbing to hypothermia or predators such as eagles, Holcomb added.

Nearly 500 of the slimed birds have been transported to the rescue center in Fairfield, California, which was specially built to care for coastal wildlife contaminated with oil. Many of the slime victims have been released.

Several hundred more birds are also being treated at facilities in Oregon and Washington State.